Alpha-dialkylthio-(dithio)-phosphoryl alpha-phenylacetic esters of cyanohydrin, and parasiticidal composition containing said esters



United States Patent Ofifice 3,030,277 Patented Mar. 5, 1963 The present invention relates to a new class of thioand dithio-phosphoric acid esters which fall within the general formula:

RO R1 P-S-CH-O OOC-CN II I l RO x R,

in which R and R are alkyl groups of a low molecular weight, R being equal to, or different from R, R R are H, alkyl, aryl radicals and X is oxygen or sulfur, and to the process for the preparation of the above mentioned esters, and also to their application as pesticides.

Laboratory tests have demonstrated that said compounds have toxic action on plant and domestic parasites. Some of them have an especially high toxic action against mites and their eggs.

The present invention is also directed to parasiticidal preparations or compositions containing or comprising compounds of the class defined by the above general formula.

where R, R" and X have the above mentioned meaning and Me is an alkali metal or is ammonium, with an a-halo u-phenylacetic ester of a cyanohydrin, of the formula:

in which Hal can be chlorine, bromine or iodine and R R have the aforesaid meaning.

The reaction can be carried out in the presence of solvents for one or both of the reactants. Ketones, particularly acetone, are very suitable solvents.

It is often advisable to use an excess of metallic dialkylphosphate. The reaction which occurs even at room temperature, can be accelerated by heating at 50-6() C. The metal halide thus formed as by-product can be removed either by filtration or by addition of water, which causes the dissolution of the inorganic salt and the contemporaneous precipitation of the desired product.

The phosphoric esters of the general Formula 1 are oily, colorless, or light yellow colored liquids, which are almost water insoluble, but are soluble in alcohol, benzene, acetone, di-oxane and in other commonly used organic solvents, with the exception of the aliphatic hydrocarbons.

The a-halo a-phenylacetic esters of cyanohydrins used as intermediate products in the preparation of compounds of the above general formula are made by adding the halide of the a-halo-phenylacetic acid to a mixture of cyanohydrin, anhydrous pyridine, and petroleum ether, the mixture being cooled at 0 C.

The temperature of the reaction mixture must always be kept at 0 C. The pyridine halide thus formed is re moved while the liquid is concentrated on a water bath under reduced pressure. The residue is diluted with methylene chloride, shaken with ice Water, and its acidity then neutralized with NaI-ICO After dehydrating the organic layer With'NaSO the substance is concentrated on a water bath. A residue consisting of the alpha-halo-phenylacetic esters of a cyanohydrin is thus obtained. The product can be purified by distilling it under vacuum.

Among the compounds comprised in the general Formula 1, the compound a-(0,0-diethyldithiophosphoryl) u-phenylacetic ester of acetoncyanohydrin, namely has shown particular effectiveness. Said compound has an acaricidal activity about 18 times that of parathion (pnitrophenyl-diethyldithiophosphate). It is a surprising fact that this new compound shows a higher parasiticidal activity than the other compounds having a similar constitution, and the phosphoric esters commonly used as parasiticides, not only against the mites of different growth stage, but on their eggs also.

The compounds of the present invention can be used in various ways. Generally, it is preferable to dilute them with solid, liquid or semi-solid carriers, i.e. wetting agents, adhesives, dispersion agents, emulsifiers can be added to form a paste. The active substances can be also dispersed in air by fumigation, or as aerosols. Other substances having insecticidal activity can be associated with them, such as phosphoric esters, dichlorodiphenyltrichloroethane, the 'y-isomer of hexachlorocyclohexane, octachloro-4-7-methane-tetrahydro-indane, etc. The invention is illustrated by the following examples, which are not intended to be limitative.

EXAMPLE 1 The present example relates to the preparation of the intermediate product, a-bromo-a-phenylacetic ester of acetoncyanohydrin, which is a new substance not described in the chemical literature. 278 grams of a-bromc-u-phem ylacetic acid bromide are slowly added to a mixture of 85 grams acetoncyanohydrin 79 grams anhydrous pyridine and 180 ml. petroleum ether, said mixture being cooled at C. The pyridine hydrobromide thus formed is removed, the liquid being concentrated on a Water bath under reduced pressure. The residue is diluted with methylene chloride, shaken with ice water and its acidity neutralized with NaHCO After dehydration of the organic layer with Na SO the mass is concentrated on a water bath. 219 g. consisting of ix-bromo-a-phenylacetic ester of acetoncyanohydrin are obtained as residue. The product can be purified by distilling it under vacuum and collecting the fraction which distills at 124 C. under 0.6 mm. Hg of pressure.

EXAMPLE 2 28.2 grams of a-bromo-a-phenylacetic ester of acetoncyanohydrin prepared according to Example 1, and dissolved in 30 ml acetone, are added to a solution of 26 g. of sodium 0,0-dimethyl-dithiophosphatedihydrate in 60 ml. acetone. Heat is released and NaBr is separated. The reaction mixture is heated under reflux for 30 minutes md, after cooling, the NaBr formed (9 g.) is removed by filtration. The liquid is concentrated under reduced pressure until the volume is reduced by half, and it is then diluted with 200 ml. Water. The oil thus separated is extracted with methylene chloride. The low acidity which develops is neutralized with the necessary amount of aqueous saturated NaHCO The organic layer is dehydrated on Na SO and the solvent is removed on a water bath.

The residue is Washed 5 times with n-hexane (with about ml. each time) by shaking it in a separatory funnel; the fraction dissolved in n-hexane is discarded. The oily liquid obtained consists substantially of Ot-(0,0-dlmethyldithiophosphoryl) a-phenylacetic ester of acetoncyanohydrin, of the structural formula.

EXAMPLE 3 28.2 grams of a-bromo-a-phenylacetic ester of acetoncyanohydrin, prepared according to Example 1, and dissolved in 30 ml. acetone, are added to a solution of 25 g. of potassium 0,0-diethyl-thiophosphate in 60 m1. acetone. The mixture is heated under reflux for 30 minutes and, after cooling, 100 ml. water are added. The mixture, if necessary, is neutralized with NaHCO and then extracted with methylene chloride. After dehydration of the organic layer with NaSO the mixture is concentrated on a water bath and the last traces of solvent are removed under reduced pressure.

26 g. of an oil are obtained, substantially consisting of a-(0,0-diethylthiophosphoryl) ot-phenylacetic acid of acetoncyanohydrin:

(EH50 (EH3 P-S-OH-CO 0+c-ON H I 0213 0 s CH3 EXAMPLE 4 28.2 grams of u-bromo-a-phenylacetic ester of aceare obtained.

Analysis: P, percent found=7.66-7.62 (the theoretical value for C H O PS N=7.99). S, percent found: l6.5816.50 (the theoretical value for C H O PS N= 16.54).

EXAMPLE 5 25.4 of a-bromo-a-phenylacetic ester of formalcyanohydrin and 25 g. of 0,0-diethyldithiopotassiumphosphate are mixed in 60 ml. acetone. A highly exothermic reaction takes place. The mixture is allowed to stand for about 20 hours at room temperature (2025 C.); most of the solvent is then evaporated under vacuum (15 mm. Hg). The residue is poured into 100 ml. water, and taken up again with 60 ml. methylene chloride. The extract in methylenechloride is washed twice with 50 ml. water, then dried on NaSO and evaporated under vacuum. The residue consists of 35 g. of a limpid straw-colored oil consisting of a-(0,0-diethyldithiophosphoryl) a-phenylacetic ester of formalcyanohydrin, of the formula:

EXAMPLE 6 25.4 grams of a-bromo-a-phenyla-cetic ester of formalcyanohydrin and 20.8 g. of 0,0-diethylthiopotassiumphosphate are mixed in 60 ml.-acetone. The mixture is allowed to stand for 20 hours. The potassium bromide formed is then filtered, and the mixture evaporated under vacuum up to constant weight. The residue consists of 32.5 g. of a light straw-colored oil which is substantially a-(*0-O-diethylthiophosphoryl) a-phenylacetie ester formal cyanohydrin:

EXAMPLE 7 38 grams of a-bromo-u-phenylacetic ester formalcyanohydrin and 36 g. of sodium 0,0-dimethyl-dithiophosphate (the hydrate salt with a titer of about 83%) are mixed in 70 ml. acetone. The reaction mixture is heated at 40-50 C. and allowed to stand for 20 hours. The solvent is evaporated under vacuum. The residue is poured into 100 ml. Water, taken up again with 60 ml. methylene chloride. The extract in methylene chloride is twice washed with 50 ml. water, dried and evaporated under vacuum. The residue (37.5 g.) is continuously extracted with n-hexane at room temperature (25-30" C.) until 32 g. of residue are obtained, after removing, under vacuum, the solvent dissolved therein. Said substance corresponds to a-(0,0-dimethyldithiophosphoryl) a-phenylacetic ester of formalcyanohydrin, of the formula:

EXAMPLE 8 20 g. of bromo-a-phenyl acetic ester of methyl-ethylketo-cyanohydrin and 19.7 g. of potassium 0,0-diethyldithiophosphate are mixed with 100 ml. of acetone. Heat is developed by the reaction and KBr is separated.

The mixture is refluxed for 20 minutes and the inorganic salt is removed by filtration. The acetone solution is concentrated under pressure; the residue is treated with 20 ml. of methylene chloride and then twice with 60 cc. of ice-cold water. After dehydration with MgSO the solvent is removed under reduced pressure thus obtaining 24 g. of a residue consisting of the m-(Qo-diethyldithiophosphoryl)-u-phenylacetic ester of methyl-ethyl-ketocyanohydrin:

in the form of an oil.

Analysis: P, 7.55%, calculated 7.72%.

EXAMPLE 9 20.2 g. of a-bromo-a-phenylacetic ester of acetalcyanohydrin and 20.2 g. of potassium diethyldithiophosphate are mixed with 100 ml. of acetone. By operating as de scribed in Example 1, 22.4 g. of an oil consisting of a- (0,0-diethyl-dithiophosphoryl)-a-phenylacetic ester of acetalcyanohydrin, are obtained.

Analysis: P, 8.13%; calculated 8.30%.

EXAMPLE 10 16 g. of a-bromo-u-phenylacetic ester of benzalcyanohydrin and 13.44 g. of potassium diethyldithiophosphate are mixed with 80 ml. of acetone. An exothermic reaction takes place with separation of KBr. The mixture is refluxed for 20 minutes and the inorganic salt is removed by filtration. The acetone solution is concentrated under vacuum, the residue is treated with 30 ml. of methylene chloride and then 3 times with 40 of ice-cold water. After dehydration with MgSO the solvent is removed under reduced pressure thus obtaining 18.8 g. of a residue consisting of a-(0,0-diethyldithiophosphoryl)-u-phenylacetic ester of benzalcyanohydrin:

Analysis: N, 3.05%; calculated 3.21.

EXAMPLE 11- 28.2 g. of a-bromo-phenylacetic ester of acetoncyano- 6 hydrin and 23 g. of potassium O-methyl-O-ethyl-dithiophosphate are mixed in the presence of 150 ml. of acetone. The reaction is exothermic, with the formation of KBr.

The mixture is refluxed for 30 minutes and is then cooled; the inorganic salt is removed by filtration. The acetone solution is concentrated under reduced pressure; the residue is treated with 50 ml. of methylene chloride and is Washed 3 times with water (60 ml. each time).

After drying on CaCl the solvent is removed under reduced pressure, thus obtaining as a residue 31.5 g. of a light reddish oil which after some time solidifies almost completely. The product, crystallized from methanol, presents a melting point of 5253.5 C.

It mainly consists of the alpha-(O-methyl-O-ethyl-dithiophosphoryl)-phenylacetic ester of acetonecyanohydrin having the formula:

P calculated: 8.29%. P found: 8.28-8.23%.

EXAMPLE 12 26.8 g. of alpha-bromophenylacetic ester of acetalcyanohydrin and 23 g. of potassium O-methyl-O-ethyldithiophosphate are mixed in the presence of 150 ml. of acetone. By operating substantially as described in Example 1, 30 g. of a reddish oil, having D =l.237 and n =1.5503, are obtained.

It mainly consists of the a-(O-methyl-O-ethyl-dithiophosphoryl)-a-phenylacetic ester of acetalcyanohydrin, having the formula:

P calculated: 8.62%. P found: 8.58-8.62%.

EXAMPLE 13 29.6 g. of bromo-phenylacetic ester of methyl-ethylketo-cyanohydrin and 23 g. of potassium O-methyl-O- ethyl-dithiophosphate are mixed in the presence of 15 0 ml. of acetone. By operating substantially as described in Example 1, 33 g. of a reddish oil, having D =l.l89 and 11 =1.5379, are obtained.

It mainly consists of alpha-(O-methyl-O-ethyl-dithiophosphoryl)-alpha-phenylacetic ester of methyl ethyl ketocyanohydrin having the formula:

P calculated: 7.99%. P found: 7.967.99%.

EXAMPLE 14 25.4 g. of alpha-bromophenylacetic ester of formalcyanohydrin and 23 g. of potassium O-methyl-O-ethyl-dithiophosphate are mixed in the presence of ml. of acetone. By operating substantially as described in Example 1, 34 g. of a reddish oil, having D =L259 and n =1.5520 are obtained.

3 It mainly consists of alpha-(O-methyl-O-ethyl-dithio- EXAMPLE 16 phosphoryl)-alpha-phenylacetie ester of forrnaleyanop hydrin, having the formula: eggs of Tetranychus telarius OH Eggs of Tetranychus telarz'us laid on young bean plants 5 were treated under standaroized conditions, with aqueous E" dispersions of the substances to be tested. Six days after OQHBO 3 treatment the lecture on the stereomicroscope was made,

and the average hatching percentage determined.

Concantr. 7 LD 05 EVALUATION on THE BIOLOGICAL ACTIVITY on THE substance g g gg COMPOUNDS OBTAINED ACCORDING TO THE FORE- ppm. percent subst, some EXAMPLES The tests prove that the products of the above general th ldithiophospholyl)- we 63 formula claimed here have technoio ically significant ina-phenylacetic ester of ccetciiey- 1,000

d 1 g t1 b1 anoliydrin 100 0 n S-CtlC1 a 1 an acaric oal properties, ma ing tern suita e hio hcs horyl)- 1000 90 1 for use in the parasite control, particularly against mites a-phenylacetie ester of acetoncyanom J 1,000 and their eggs. The following tabulation of test results ilhydm" 200 100 lustrates this. a-(0, o-ci tiiy iitii o h s h ryn- 12 go I (2-!) my see 10 es er 0 see oneyano- 5 55 EXAMPLE 15 hydrm 5 79 52 T etranychus telarius L. 11-(0,o-diethyldithiODhOSPhMYD- 1 000 2 I a-plicnylaeetic ester of formalcyanc- 100 0 1, 000 A mixed population of Tetranychus telarzus in various hydmh.

a-(0,0-diethylthiophosphoryn-a- 1 000 2 stages of growth of bean plants was treated under standghednylacetic ester offormal yano 0 1,000

n y rm ardized conditions with aqueous dispersions of the com 0M0(Mimethyldithiophosphoryu 1 D00 32 pounds to be tested. 24 hours after treatment, the average a-phenylacetic ester or iormalcyano- O 1,000 mortality percentage were as follows: 1 000 100 100 as Compound A g2 93 Ooncentr. LD 95 12 5 5:

active Mortalconcentr. f 5 Substance subst., ity, active 1 15 p.p.m. percent subst., C p d B 100 2 p.p.m.

Compound 0 100 10 100 1,000 100 a-(O-O-dimethyldit;hiophosphoryl)- 5 91 a-phenylacetic ester of acetoney- 2.5 66 5.8 y yl-dtet y p 125 90 anohydrin. 1. 25 11 phoryD-a-phenylacetic ester of 62 75 23 0.62 0 acetone cyanohydrin. 31 2 8g 10 as a-(O-O-diethylthlophosphoryl) 8 12 a-phenylecetic ester of acetong 4 40 1'(o'methyl'o'ethYl'dithmphospho' 1 000 11 cyanohydrin ry1)-a-phen y1aeetic ester of acetal 0 1, 000

eyanohydrin. 100 400.0 99 a-(O-O-diethyldithlophosphory1)- 0. e2 99 a-(O-methyl-0-ethy1-dit i0p D 8 a-phenylaeetie ester of aeeton- 0. 31 so 0. 42 ryll-a-phenylaeeuc ester of et yl 0 66 29 cyanohydrin. 0. 16 50 yl-k ya yd 0 47 108.08 5 12' 5 2s a- 0-oii thy dit i p sp ry1) 50 9 $333?tttifitt2323 03553,;'

ggggg 'gg fg ester of formal 5 63 cyanohydrin 1, 000 4 1,000

6.2 5 80 100 a-(O-O-dlethylthiophosphoryl) 1 ,8 5O EXAMPLE 17 a-phenylaeetie ester of iormalcyi 51 28 anoliydrin. 5 14 Tetranychus telarms L.

1, g 100 Comparison of the parasiticidal activity of p-nitroa-(O-O-dimethyldithlophosphoryl) flag phenyl-diethyldithiophosphate (parathion) with that of a-pllilenyiacetic ester of iormalcy- 50 120 a-(0,0-diethylphosphoryl) tit-acetic ester of acetoncyanoano ydrin. 23 JD hydrin: a-(O-O-diethyldithiophosphoi-yl) 3g a-phenylacetic ester of methyl- 25 93 L 5 Acaticidal ggigg gf ydnn (com' (25g Congentr. M LD 95 aegwgly 80 1V8 01'- 00110. W1 28. 8 133 Substance subst., tality,t acgite elqual .in. Green S11 S a-(O-O-diethyldithiophosphory1)- 20 0 92 p p p p.p.m: of 8:; a-phenylacetic ester of acetal- 10.0 85 23 thion) eyanohydrin (compound B). 5.0 67 2. 50 4s 1. 25 23 20 100 -(0-0-diethyldlth10phosphory1)- I 1, 000 100 10 98 a-phenylacetic ester of benzal- 100 28 1, 000 p-Nitrophenyldiethyldithio- 6 eyanohydrin (compound 0). 10 0 phosphate (Parathion). 0.5 33 10 a-(O-methy1-O-etl1y1dith1ophosgg 1 phoryn-a-phenyl-acetic ester 0! 25 43 0. 53 25 8 0 42 1 785 acemnecyamhydrmg a-((%50-difithyfiditliiophtgsphg- 01 02 99 -(O methy1 O ethymithiophos ry a-p eny ace ic es er 0 0. 31 89 a phoryD-a-phenyl-acetie ester of 0.6 70 acetoncy anohydtm' 8 methyl-ethyl-ketocyanohydrin. 125 17 00 & I v 1000 100 2150 06 o;-(O-methyl-O-dithiopliosphoryl)- 5O 0 96 r 48 Compound A..-...... 1. 25 93 1. 5 500 a-phenylacetic ester of tormal- L 25.0 '63 0. 62 63 eyanohydrin. 12. 5 11 0 31 20 EXAMPLE 18 Eggs of Tetranychus telarius Comparison of the activity of p-chlorobenzene sulphomate of p-chlorobenzene snlphonate of p-chlorophenyl with that of a-(0,0-diethyldithiophosphoryl)-a-phenylacetic ester of cyanohydrin:

M usca domestica L.

Upon topical application, by means of a microsyn'ne, of acetone solutions of the product under examination on five days old female flies, the following results have been obtained:

Dose, Percent DL 50, Substance /ily mortality /fiy 20 hours a- (0,0-dimothyldithiophosphoryl) -or- 4 92 ghenylaeetie ester of aeetoncyanohy- 2 40 2.2

1.00 95 a-(O-O-diethylthiophosphoryl)-a-phen- 0.75 79 53 ylaeetic ester of acetoneyanohydrin.

a (0,0 diethyldithiophosphoryl) oz 0. 8 80 phenylacetie ester of aeetoncyanohy- 0.6 68 0. 52 drin. 0. 45 33 a (0,0 diethyldithiophosphoryl) a 0. 7 S6 phenylaeetic ester of iornialeyanohy- 0.525 59 0.5 drin. 0. 393 20 0.5 08 a-(0,0-diethylthiophosphoryD-a-phen- 0.375 88 0 25 ylacetie ester of formaleyanohydrin. 0. 281 64 0.210 29 2.00 100 oz- (0,0-dirnethyldithiophosphoryl) -a- 1. 50 88 1 07 phenylaeetic ester of iormaleyanohy- 1. 25 63 drin. 0. 84 25 0. 93 89 Compound A 0.70 42 0. 72

0.525 B. 6 1 79 Compound B 0.75 35 0.82

0. 56 10 Compound 0 4 40 4 a-(O-methyl-O-ethyldithio-phosphoryl) gg u-phenylaeetic esters of aeetonecyano- 67 0.75 hydrin (Ex. 11).

0. 63 34 7.00 100 a- (0 -methyl- 0 ethyl-dithlophospho 5. 33 94 ry1)--pheny1-acetic ester aeetalcya- 4.00 77 2. 7 nohydrin (Ex. 12). 3.00 01 2.25 32 2. 66 100 a- (O-methy1-ethyl-dithiophosphoryl) 2.00 98 a-phenyl acetic ester of methyl-ethyl 1. 50 85 1.03 ketocyanohydrin (Ex. 13). 1.12 61 0. 84 25 1. 060 100 a- (0 -methyl- 0 -ethy1-dithiophospho 0. 800 89 ryl)-a-phenyl acetic ester of formal 0. 600 67 0. 52 cyanohydrln (Ex. 14). 0. 450 29 0. 337 10 EXAMPLE 20 Aphzs fabae 'I he insects are bred on bean plants under artificial 101 light, under standardized conditions. The population of aphides is nebulized with suitably formulated aqueous dispersions of the compounds considered:

Coneentr. Percent Substance active mortality LD subst., 24hours ppm.

oz- (0, O -dimethyl-dithiophosphoryl) -azphenylaeetie ester of acetoncyanohy- (lrin.

a-(0,0-dlethylthiophosphoryl)-a-phenylacetic ester of aeetoncyanohydrin.

HNOI

phenylacetic ester of formaleyanohy- 64 drin.

a-(O-O di6t11Yl-(IithlOphOSphOl'Yl)-a irenylaeetie ester of aeetoneyanohya-(O-O-diethyl-dithiophosphoryl)-aa-(O-O-dimethyl-dithiophosphoryl)ax- Elrenylaeetie ester of tormaleyanohy- 1, 000 Compound A 108 l 1, 000 Compound 13 108 100 Compound C; 100

100.0 a-(O-methyl-O-ethyl-dithiophosphoryl)- 50. 0

lz-phenylaeetie ester of aeetone-eyano- 25.0 78 hydrin (Ex. 11). 12. 5 6.2 a-(O-methyl-O-ethyl-dithiophosphoryl)- 1 000 wphenylacetie ester of aeetalcyanohy- 500 1, 000 drin (Ex. 12). a-(O-methyl-O-ethyl-dithiophosphoryl)- a-phenylacetie ester of methyl-ethyl- 100 260 ketoeyanohydrin. 50 a-(O-n1ethyl-O-ethyl-dithiophosphoryl)- 8 rx-phenyl-aeetic ester of formaleyano- 0 42 hydrin (Ex. 14). 5

EXAMPLE 21 Determination of the acute toxicity on the rat per 0s and endovenous injection of the a-(0,0-diethyldithioph sphoryl)-oc-phenylacetic ester 0]" acetoncyanohydrin The product was dissolved in dimethylacetamide, the Single groups of animals tested being half females and half males. LD 50, 0s 45 mg./kg. LD 50, venous 40 mg./kg.

The compounds in which either or both R and R are C H and/or C H are generally made in the same way from the eyanohydrin of the corresponding aldehyde, or ketone.

By choice of the corresponding aldehyde or ketone cyanohydrin, the radical can further be as follows a 11 We claim: 1. A'parasiticidal compound of the formula:

RO\ R1 t -s-oH-o0- 'J-oN RO x R:

in which R and R" are alkyl groups of low molecular weight, R being the same as or different from R"; R and R are taken from the group consisting of H, CH C H and C l-I and X is taken from the group consistting of S and O.

2. A compound of the formula:

I i Hal-(!3H-COOO-CN in which Ha'l is taken from the class consisting of chlorine, bromine, and iodine, and R R are taken from the class consisting of H, CH C H and C H 3. A parasiticidal composition containing at least one of the compound defined in claim 1, mixed with a compound of another class of insecticides, and with an inert substance, and a fertilizer compound.

4. A parasiticide, u-(O,O-diethyldithiophosphoryl)-04- phenylacetic ester of acetoncyanohydrin, of the formula:

5. A parasiticide a-(0,0-diethyldithiophosphoryl)-aphenylacetic ester of methyl-ethyl-ketocyanohydrin, of the formula:

6. An acaricidal composition containing the compounds defined in claims 4 and 5, mixed with another ester of the class defined in claim 1, and with a commonly used insecticide, and mixed with an inert substance, and with a fertilizer compound.

7. In the art of contnolling mites, the improvement 12 comprising applying to a locality subject to infestation thereby a compound of the formula:

in which R and R" are alkyl groups of low molecular weight, R being the same as or diiferen't from R, R and R are taken from the group consisting of H, CH C H and C H and X is taken from the group consisting of S and O.

8. In the art of controlling insects, the improvement comprising applying to a locality subject to infestation thereby a compound of the formula:

FWD/INK in which R and R" are alkyl groups of low molecular weight, R being the same as or difierent from R", and R and R are taken from the group consisting of H, CH C H and C H (and X is taken from the gnoup consisting of S and O.

9. In the art of controlling mites, the improvement comprising applying to the locality subject to infestation thereby compounds of the group consisting of those defined in claims 4 and 5.

10. u. (O-methyl-O-ethyl-dithiophosphoryl)wit-phenylacetic ester of acetoncyanohydrin.

11. oz (O-methyl-O-ethy1-dithioplrosphoryl)-a-phenylacetic ester of acetalcyanohydrin.

12. a (O-methyl-O-ethyl'dithiophosphoryl)-a-pheny1- acetic ester of methyl-ethyl-ketocyanohydrin.

13. a (O methyl-O-ethyl-dithiophosphoryl)-a-phenylacetic ester of formalcyanohydrin.

References Cited in the file of this patent UNITED STATES PATENTS 2,494,284 Cassaday et a1 Jan. 10, 1950 2,947,662 Fusco et a1. Aug. 2, 1960 2,954,318 Ludvik Sept. 27, 1960 2,956,921 Santmyer Oct. 18, 1960 2,971,974 Blair Feb. 14, 1961 2,977,382 Millikan Mar. 28, 1961 OTHER REFERENCES Cyanohydrins, Tech. Bull. SP-133, by Rohm & Haas Co, Washington Square, Philadelphia 5, Pa (January 1957), page 8.

Royals: Advanced Organic Chemistry, Prentice-Hall, Inc., Englewood Cliffs, NJ. 1956), page 605. 

1. A PARASITICIDAL COMPOUND OF THE FORMULA: 